Thermodynamic properties of MgSiO3 perovskite derived from large scale molecular dynamics simulations

A molecular dynamics simulation study of MgSiO₃ has been performed using a large sample containing 4096 unit cells. Thermodynamic properties have been extracted using a semiclassical approximation to the correct quantum mechanical treatment, using the calculated density of states and the quantum harmonic formalism for thermodynamic functions. Simulations performed at different temperatures and volumes have given an estimate of the relative contributions due to thermal expansion (quasi-harmonic effects) and direct anharmonic interactions. Comparison of results for mean square atomic displacements with results on smaller samples have shown the limitations of smaller sample sizes.